RESUMEN
In order to enhance second-harmonic generation (SHG) efficiency in a waveguide-coupled photonic nanocavity, we introduce a reflector at the edge of the waveguide and investigate its influence on input power and SHG efficiency. SHG efficiency and critical input power of the reflective waveguide-coupled cavity are controlled by the reflection amplitude and phase delay of the reflector. At input powers considerably lower than the critical power, SHG efficiency increases by up to three orders of magnitude higher than the case without reflector. Moreover, SHG efficiency of 100% at critical input power, which is twice that of the previous result, can be achieved over a wide phase range. These results prove the feasibility and controllability of highly efficient nonlinear optical devices.
RESUMEN
We theoretically investigate the optical characteristics of a thin-film photonic crystal structure with a complete photonic bandgap for both polarization of the transverse electric and transverse magnetic modes for any in-plane direction. The structure consists of three-layer stacked two-dimensional photonic crystal slabs, and the thickness of the structure is less than a few wavelengths. We show that a wide complete photonic bandgap can be obtained in the asymmetrically stacked photonic crystal structure. In addition, we designed a waveguide with a broad bandwidth of 100 nm and a nanocavity with a quality factor of 3.7 × 107 in the structures.
RESUMEN
Measurement of optical loss in nanophotonic waveguides is necessary for monitoring the properties of integrated photonic devices. We propose a simple method of measuring the optical loss using integrated nanocavities. It is shown theoretically that weak coupling between the waveguide and cavities leads to a direct estimation of the optical loss by measuring light radiated from the cavities. In addition, we experimentally demonstrate the optical loss in a fabricated photonic crystal waveguide. Our method gives not only a degree of freedom in real-time monitoring of the optical properties of nanophotonic structures, but it also can be used for various waveguide-based applications.
RESUMEN
A transformation-optics wedge waveguide designed for the simultaneous collection and directional collimation of pulsed dipole radiation is described and tested with numerical simulation. Azimuthal compression of free space toward a narrow fan-shaped waveguide sector allows dipole pulse radiation in free space to be transformed into a directional non-dispersive pulse propagating within that sector. The collection and collimation ability of the proposed structure is compared with classical approaches using metallic wedge mirrors and parabolic mirrors, which inherently allow multiple internal reflections and thus generate significant pulse distortion and low light-collection efficiency. It is shown that the optical pulse generated by the dipole and propagated through the proposed transformation-optics waveguide maintains its original shape within the structure, and demonstrates enhanced optical power.